Detect GCC compile-time flags of a binary

Question

Is there a way to find out what gcc flags a particular binary was compiled with?

Answer 1

I don't think so.

You can see if it has debug symbols, which means -g was used ;) But I can't think of any way how you could find out which directories have been used to search for include headers for example.

Maybe a better answer is possible if you only target for a specific flag; e.g. if you only want to know if the flag "..." was set when this binary was compiled or not. In that case, what flag would this be?

Answer 2

A quick look at the GCC documentation doesn't turn anything up.

The Boost guys are some of the smartest C++ developers out there, and they resort to naming conventions because this is generally not possible any other way (the executable could have been created in any number of languages, by any number of compiler versions, after all).

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(Added much later): Turns out GCC has this feature in 4.3 if asked for when you compile the code:

A new command-line switch -frecord-gcc-switches ... causes the command line that was used to invoke the compiler to be recorded into the object file that is being created. The exact format of this recording is target and binary file format dependent, but it usually takes the form of a note section containing ASCII text.

Answer 3

I'm the one who asked Brian to post this originally. My question had to do with the samba binary. I found out that you can run smb -b to get information on how it was built.

Answer 4

Experimental proof:

diciu$ gcc -O2 /tmp/tt.c -o /tmp/a.out.o2
diciu$ gcc -O3 /tmp/tt.c -o /tmp/a.out.o3
diciu$ diff /tmp/a.out.o3 /tmp/a.out.o2 
diciu$

I take that as a no as the binaries are identical.